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Seasonic X-Series 660W review

Our Rating :
Price when reviewed : £131
inc VAT

High efficiency, great design and very quiet, this is a great high-end PSU

When you spend this much on a power supply, you really it want it to do absolutely everything. Fortunately, the Seasonic X-Series 660W delivers.

For starters, this PSU is 80 Plus Gold certified, which means efficiencies of at least 87 per cent at all loads. In our tests, we suffered no problems and the power supply managed at impressive above-specification efficiency of 88.58 per cent at 100 per cent load, 90.77 per cent efficiency at 50 per cent load and 88.41 per cent at 20 per cent load. This means some decent savings over 80 Plus Bronze or Silver certified power supplies.

Seasonic X-Series 660W

The 80 Plus Gold certification shows its worth with these high efficiencies

Not only is this power supply efficient, it’s also quiet. There’s just a single 120mm fan, which is really quiet, even at high loads. Even better, when the PSU is at 25C or less, the fan shuts down completely for a completely quiet power supply.

As you’d expect at this price, the X-Series 660W has a completely modular design, even down to the required 24-pin motherboard connector. There’s plenty of choice on offer with five Molex, eight SATA and two floppy power connectors. There’s just two 6+2 pin PCI Express connectors, so dual-card configurations are out, although you’ll happily be able to run the most powerful single cards.

Seasonic X-Series 660W

There’s no getting away from the fact this is an expensive power supply, but you certainly get a lot for the money, including a generous five-year warranty. With its fully-modular design, high efficiency and silent running, it’s a great choice for a high-end PC and wins an Ultimate award.


Price £131
Rating *****
Award Ultimate


Size 150x160x86mm
Standard ATX
PFC active
Fans 1x 120mm bottom
Fan control automatic

Claimed Output

3.3V rail 25A
5V rail 25A
Power supply wattage 660W
SLI certified no
CrossFire certified no


Modular yes
Molex connectors 5
Floppy disk power connectors 2
SATA power connectors 8
4-pin CPU power connectors 1
8-pin CPU power connectors 1

Buying Information

Price £131
Warranty five years RTB

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